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Uncommon Link.EXE Parent Process — Sigma Rule

Sigma rule 6e968eb1-5f05-4dac-94e9-fd0c5cb49fd6. Uncommon Link.EXE Parent Process — Sigma Rule. Detects an uncommon parent process of "LINK.EXE". Link.EXE in Microsoft incremental linker. Its a utility usually bundled with Visual Studio installation. Multiple utilities often found in the same folder (editbin.exe, dumpbin.exe, lib.exe, etc) have a hardcode call to the "LINK.EXE" binary without checking its validity. This would allow an attacker to sideload any binary with the name "link.exe" if one of the aforementioned tools get executed from a different location. By filtering the known locations of such utilities we can spot uncommon parent process of LINK.EXE that might be suspicious or malicious.

Rule metadata and linked tags

testmediumprocess_creationwindowsattack.stealthattack.t1218

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: medium. Source dates: 2022-08-22 / 2024-06-27.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 4658cdff0a56722fca9212229d6896bb7e7c956a9325869565e0787218a2e7c4

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Uncommon Link.EXE Parent Process
id: 6e968eb1-5f05-4dac-94e9-fd0c5cb49fd6
status: test
description: |
    Detects an uncommon parent process of "LINK.EXE".
    Link.EXE in Microsoft incremental linker. Its a utility usually bundled with Visual Studio installation.
    Multiple utilities often found in the same folder (editbin.exe, dumpbin.exe, lib.exe, etc) have a hardcode call to the "LINK.EXE" binary without checking its validity.
    This would allow an attacker to sideload any binary with the name "link.exe" if one of the aforementioned tools get executed from a different location.
    By filtering the known locations of such utilities we can spot uncommon parent process of LINK.EXE that might be suspicious or malicious.
references:
    - https://twitter.com/0gtweet/status/1560732860935729152
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-22
modified: 2024-06-27
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\link.exe'
        CommandLine|contains: 'LINK /' # Hardcoded command line when we call tools like dumpbin.exe, editbin.exe, lib.exe...etc
    # Add other filters for other legitimate locations
    filter_main_visual_studio:
        ParentImage|startswith:
            - 'C:\Program Files\Microsoft Visual Studio\'
            - 'C:\Program Files (x86)\Microsoft Visual Studio\'
        ParentImage|contains:
            - '\VC\bin\'
            - '\VC\Tools\'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

Original YAML and metadata in JSON

False positives

  • Unknown

Source references

Connected ecosystem references

Exact source-tagged techniques

Telemetry review

Read the original logsource above, then inspect the linked detection workspaces for technique-level sensor context. No per-rule telemetry equivalence is inferred.

Pinned research references. No browser attack runner, live simulation result or validated detector is asserted. Source mappings and validation limits are preserved. ATT&CK / Atomic provenance · Detection provenance.